Long & short radius elbow chart · 90° & 45° · NPS ½–48 · mm & inch · tolerances · calculator
Quick answer
Pipe elbow dimensions for ASME B16.9 butt-weld elbows are given as center-to-end lengths: the 90° long-radius (LR) center-to-end dimension A equals 1.5 × NPS in inches for NPS ¾ and larger (NPS 6 → 9.00 in / 229 mm). A 90° short-radius (SR) elbow has C = 1.0 × NPS and is tabulated for NPS 1–24 only. A 45° LR elbow is not half of A — read B from the table.
Key facts — pipe elbow dimensions
- 90° LR elbow: A = 1.5 × NPS (in) from NPS ¾ up; NPS ½ is the exception and shares A = 38 mm (1.50 in) with NPS 1.
- 90° SR elbow: C = 1.0 × NPS (in), listed in ASME B16.9 for NPS 1 to 24 only.
- 45° LR elbow: B ≈ A × tan 22.5° (≈ 0.414 A) from about NPS 3½ up; smaller sizes are deliberately longer.
- 180° return: center-to-center O = 2 × A (LR) or 2 × C (SR).
- Tolerance on A, B, C: ±0.06 in (≈ ±1.5 mm) for NPS ½–8, rising to ±0.19 in (≈ ±4.8 mm) for NPS 32–48.
- Current edition: ASME B16.9-2024, which also carries the short-radius elbows and returns of the withdrawn ASME B16.28.
What is a butt-weld pipe elbow?
A pipe elbow is a curved fitting that turns a line through a fixed angle — usually 90° or 45° — while keeping the same bore as the pipe. Butt-weld (buttwelding) elbows — one of the main types of pipe fittings — have beveled ends that are welded directly to the pipe, so the fitting becomes part of the pressure boundary. Pipe elbow dimensions, tolerances and marking are set by ASME B16.9, which covers factory-made wrought fittings from NPS ½ to NPS 48 (DN 15–1200).
Three families matter in day-to-day design and fabrication:
- Long radius (LR, 1.5D): centerline radius 1.5 × NPS. The default in almost every piping class.
- Short radius (SR, 1.0D): centerline radius equal to NPS. Used where space is tight; 90° only.
- 3D, 5D and larger bends: not tabulated in B16.9. They are ordered to project data sheets — for pipelines, typically as induction bends to ASME B16.49.
How to read pipe elbow dimensions
Every center-to-end dimension is measured from the tangent-line intersection — the point where the extended centerlines of the two legs cross — to the face of the welding end. That is why the same number is used for both legs of a 90° elbow, and why it can be taken straight off a piping isometric.
- NPS / DN
- Nominal pipe size (inch designation) and nominal diameter (metric designation). Neither is a measured diameter.
- OD
- Outside diameter at the welding bevel. It matches the pipe OD of ASME B36.10M / B36.19M so the ends line up for welding. See what an industrial pipe is for NPS and schedule basics.
- A
- Center-to-end of a 90° long-radius elbow: from the point where the two leg centerlines meet (tangent-line intersection) to the welding end.
- B
- Center-to-end of a 45° long-radius elbow, measured the same way.
- C
- Center-to-end of a 90° short-radius elbow.
- R
- Centerline bend radius: 1.5 × NPS for LR and 1.0 × NPS for SR (nominal).
- T
- Wall thickness at the welding end. It is ordered to match the connecting pipe schedule or a specified wall.
Pipe elbow dimensions chart — ASME B16.9 (mm)
Table 1 lists pipe elbow dimensions for every size from NPS ½ to 48. A dash means that fitting is not tabulated in ASME B16.9 — not that it is impossible to buy. Use the inch table (Table 2) when your drawings are in imperial units; the SI and inch values are separate tables in the standard and are already rounded independently, so do not convert one into the other for inspection.
| NPS (in) | DN | OD (mm) | 90° LR — A (mm) | 45° LR — B (mm) | 90° SR — C (mm) |
|---|---|---|---|---|---|
| 1/2 | 15 | 21.3 | 38 | 16 | — |
| 3/4 | 20 | 26.7 | 29 | 11 | — |
| 1 | 25 | 33.4 | 38 | 22 | 25 |
| 1 1/4 | 32 | 42.2 | 48 | 25 | 32 |
| 1 1/2 | 40 | 48.3 | 57 | 29 | 38 |
| 2 | 50 | 60.3 | 76 | 35 | 51 |
| 2 1/2 | 65 | 73.0 | 95 | 44 | 64 |
| 3 | 80 | 88.9 | 114 | 51 | 76 |
| 3 1/2 | 90 | 101.6 | 133 | 57 | 89 |
| 4 | 100 | 114.3 | 152 | 64 | 102 |
| 5 | 125 | 141.3 | 190 | 79 | 127 |
| 6 | 150 | 168.3 | 229 | 95 | 152 |
| 8 | 200 | 219.1 | 305 | 127 | 203 |
| 10 | 250 | 273.1 | 381 | 159 | 254 |
| 12 | 300 | 323.8 | 457 | 190 | 305 |
| 14 | 350 | 355.6 | 533 | 222 | 356 |
| 16 | 400 | 406.4 | 610 | 254 | 406 |
| 18 | 450 | 457.0 | 686 | 286 | 457 |
| 20 | 500 | 508.0 | 762 | 318 | 508 |
| 22 | 550 | 559.0 | 838 | 343 | 559 |
| 24 | 600 | 610.0 | 914 | 381 | 610 |
| 26 | 650 | 660.0 | 991 | 406 | — |
| 28 | 700 | 711.0 | 1067 | 438 | — |
| 30 | 750 | 762.0 | 1143 | 470 | — |
| 32 | 800 | 813.0 | 1219 | 502 | — |
| 34 | 850 | 864.0 | 1295 | 533 | — |
| 36 | 900 | 914.0 | 1372 | 565 | — |
| 38 | 950 | 965.0 | 1448 | 600 | — |
| 40 | 1000 | 1016.0 | 1524 | 632 | — |
| 42 | 1050 | 1067.0 | 1600 | 660 | — |
| 44 | 1100 | 1118.0 | 1676 | 695 | — |
| 46 | 1150 | 1168.0 | 1753 | 727 | — |
| 48 | 1200 | 1219.0 | 1829 | 759 | — |
Pipe elbow dimensions chart — ASME B16.9 (inch)
| NPS (in) | DN | OD (in) | 90° LR — A (in) | 45° LR — B (in) | 90° SR — C (in) |
|---|---|---|---|---|---|
| 1/2 | 15 | 0.840 | 1.50 | 0.62 | — |
| 3/4 | 20 | 1.050 | 1.12 | 0.44 | — |
| 1 | 25 | 1.315 | 1.50 | 0.88 | 1.00 |
| 1 1/4 | 32 | 1.660 | 1.88 | 1.00 | 1.25 |
| 1 1/2 | 40 | 1.900 | 2.25 | 1.12 | 1.50 |
| 2 | 50 | 2.375 | 3.00 | 1.38 | 2.00 |
| 2 1/2 | 65 | 2.875 | 3.75 | 1.75 | 2.50 |
| 3 | 80 | 3.500 | 4.50 | 2.00 | 3.00 |
| 3 1/2 | 90 | 4.000 | 5.25 | 2.25 | 3.50 |
| 4 | 100 | 4.500 | 6.00 | 2.50 | 4.00 |
| 5 | 125 | 5.563 | 7.50 | 3.12 | 5.00 |
| 6 | 150 | 6.625 | 9.00 | 3.75 | 6.00 |
| 8 | 200 | 8.625 | 12.00 | 5.00 | 8.00 |
| 10 | 250 | 10.750 | 15.00 | 6.25 | 10.00 |
| 12 | 300 | 12.750 | 18.00 | 7.50 | 12.00 |
| 14 | 350 | 14.000 | 21.00 | 8.75 | 14.00 |
| 16 | 400 | 16.000 | 24.00 | 10.00 | 16.00 |
| 18 | 450 | 18.000 | 27.00 | 11.25 | 18.00 |
| 20 | 500 | 20.000 | 30.00 | 12.50 | 20.00 |
| 22 | 550 | 22.000 | 33.00 | 13.50 | 22.00 |
| 24 | 600 | 24.000 | 36.00 | 15.00 | 24.00 |
| 26 | 650 | 26.000 | 39.00 | 16.00 | — |
| 28 | 700 | 28.000 | 42.00 | 17.25 | — |
| 30 | 750 | 30.000 | 45.00 | 18.50 | — |
| 32 | 800 | 32.000 | 48.00 | 19.75 | — |
| 34 | 850 | 34.000 | 51.00 | 21.00 | — |
| 36 | 900 | 36.000 | 54.00 | 22.25 | — |
| 38 | 950 | 38.000 | 57.00 | 23.62 | — |
| 40 | 1000 | 40.000 | 60.00 | 24.88 | — |
| 42 | 1050 | 42.000 | 63.00 | 26.00 | — |
| 44 | 1100 | 44.000 | 66.00 | 27.38 | — |
| 46 | 1150 | 46.000 | 69.00 | 28.62 | — |
| 48 | 1200 | 48.000 | 72.00 | 29.88 | — |
Elbow dimension & cut-length calculator
This calculator turns the pipe elbow dimensions above into shop numbers. Pick a size and elbow type to get the standard center-to-end, centerline radius and marking arcs. Enter an angle to mark an odd-angle elbow from a 90° LR, or a center-to-center distance to get the pipe cut length between two fittings.
Values from ASME B16.9-2024 tables. Arc lengths use nominal R; verify with a template on site.
Rules of thumb — and where they break
Fitters often work out elbow take-outs mentally. The shortcuts below are reliable for the ranges stated; outside those ranges, always read the table.
- A = 1.5 × NPS × 25.4 mm matches the table within 1 mm from NPS ¾ to 48. It fails only at NPS ½, which is 38 mm rather than 19 mm, because the fitting needs enough length to form and weld.
- C = NPS × 25.4 mm matches the SR table from NPS 1 to 24.
- B = A × tan 22.5° (≈ 0.414 A) is within about 4 mm from NPS 3½ upward. Below that the standard values are longer — NPS 1 is 22 mm against a geometric 16 mm.
- 180° return center-to-center is 2A (LR) or 2C (SR). For an NPS 6 LR return: 2 × 228.6 ≈ 457 mm, the tabulated value.
ASME B16.9 dimensional tolerances for elbows
Nominal pipe elbow dimensions are only half of an inspection; the tolerances below apply to the finished fitting. They are tabulated in inches in the standard; Table 3a repeats them as a direct millimeter conversion for shop use. All values are ± unless shown otherwise.
| NPS | OD at bevel | ID at end | Center-to-end A, B, C, M | 180° return C-C (O) | 180° return back-to-face (K) | Return end alignment (U) |
|---|---|---|---|---|---|---|
| 1/2 – 2 1/2 | +0.06 / −0.03 | 0.03 | 0.06 | 0.25 | 0.25 | 0.03 |
| 3 – 3 1/2 | 0.06 | 0.06 | 0.06 | 0.25 | 0.25 | 0.03 |
| 4 | 0.06 | 0.06 | 0.06 | 0.25 | 0.25 | 0.03 |
| 5 – 8 | +0.09 / −0.06 | 0.06 | 0.06 | 0.25 | 0.25 | 0.03 |
| 10 – 18 | +0.16 / −0.12 | 0.12 | 0.09 | 0.38 | 0.25 | 0.06 |
| 20 – 24 | +0.25 / −0.19 | 0.19 | 0.09 | 0.38 | 0.25 | 0.06 |
| 26 – 30 | +0.25 / −0.19 | 0.19 | 0.12 | — | — | — |
| 32 – 48 | +0.25 / −0.19 | 0.19 | 0.19 | — | — | — |
| NPS | OD at bevel | ID at end | Center-to-end A, B, C, M | 180° return C-C (O) | 180° return back-to-face (K) | Return end alignment (U) |
|---|---|---|---|---|---|---|
| 1/2 – 2 1/2 | +1.5 / −0.8 | ± 0.8 | ± 1.5 | ± 6.4 | ± 6.4 | ± 0.8 |
| 3 – 3 1/2 | ± 1.5 | ± 1.5 | ± 1.5 | ± 6.4 | ± 6.4 | ± 0.8 |
| 4 | ± 1.5 | ± 1.5 | ± 1.5 | ± 6.4 | ± 6.4 | ± 0.8 |
| 5 – 8 | +2.3 / −1.5 | ± 1.5 | ± 1.5 | ± 6.4 | ± 6.4 | ± 0.8 |
| 10 – 18 | +4.1 / −3.0 | ± 3.0 | ± 2.3 | ± 9.7 | ± 6.4 | ± 1.5 |
| 20 – 24 | +6.4 / −4.8 | ± 4.8 | ± 2.3 | ± 9.7 | ± 6.4 | ± 1.5 |
| 26 – 30 | +6.4 / −4.8 | ± 4.8 | ± 3.0 | — | — | — |
| 32 – 48 | +6.4 / −4.8 | ± 4.8 | ± 4.8 | — | — | — |
| NPS | Off-angle Q (in) | Off-angle Q (mm) | Off-plane P (in) | Off-plane P (mm) |
|---|---|---|---|---|
| 1/2 – 4 | 0.03 | 0.8 | 0.06 | 1.5 |
| 5 – 8 | 0.06 | 1.5 | 0.12 | 3.0 |
| 10 – 12 | 0.09 | 2.3 | 0.19 | 4.8 |
| 14 – 16 | 0.09 | 2.3 | 0.25 | 6.4 |
| 18 – 24 | 0.12 | 3.0 | 0.38 | 9.7 |
| 26 – 30 | 0.19 | 4.8 | 0.38 | 9.7 |
| 32 – 42 | 0.19 | 4.8 | 0.50 | 12.7 |
| 44 – 48 | 0.18 | 4.6 | 0.75 | 19.0 |
Elbow take-out and pipe cut length
The most common shop use of pipe elbow dimensions is the take-out. On an isometric, a run between two elbows is dimensioned center-to-center. The pipe you actually cut is shorter by each fitting’s center-to-end (its take-out) and by the root gap at every butt weld.
Worked example — NPS 4 spool
- Isometric center-to-center: 1500 mm; two 90° LR elbows; root gap 3 mm per weld.
- Take-out per elbow A = 152 mm (Table 1).
- Cut length = 1500 − 152 − 152 − (2 × 3) = 1190 mm.
- If one elbow were SR (C = 102 mm): 1500 − 152 − 102 − 6 = 1240 mm.
Cutting a 90° LR elbow to an odd angle
When a route needs, say, 30° or 60°, fabricators often cut it from a 90° LR elbow. The cut must lie on a radial line through the arc center, and the new center-to-end follows directly from the bend radius.
Worked example — 30° from an NPS 6 LR elbow
- R = 1.5 × 6 × 25.4 = 228.6 mm; OD = 168.3 mm; θ = 30° = 0.5236 rad.
- New center-to-end = 228.6 × tan 15° = 61.3 mm.
- Mark along the outer arc (R + OD/2) × θ = 163.8 mm and the inner arc (R − OD/2) × θ = 75.6 mm from the welding end, then join the marks around the circumference.
- For reference, the full 90° outer and inner arcs of the same elbow are 491.3 mm and 226.9 mm.
Odd-angle cuts are not covered by standard pipe elbow dimensions, so record them on the spool drawing. Re-bevel the cut end to the welding procedure and check the angle with a protractor before fit-up. A cut elbow loses its factory marking at that end, so transfer the heat number before cutting if your quality plan requires traceability.
Long radius vs short radius: how to choose
| Criterion | Long radius (LR, 1.5D) | Short radius (SR, 1.0D) |
|---|---|---|
| Center-to-end (90°) | 1.5 × NPS — e.g. NPS 6: 229 mm | 1.0 × NPS — e.g. NPS 6: 152 mm |
| Size range in B16.9 | NPS ½ – 48 (90° and 45°) | NPS 1 – 24 (90° only) |
| Pressure loss (Crane TP-410 L/D) | ≈ 14 f_T (NPS 6: K ≈ 0.21) | ≈ 20 f_T (NPS 6: K ≈ 0.30) — about 40 % higher |
| Stress intensification | Lower (larger flexibility characteristic h) | Higher — NPS 6 Sch 40 in-plane i ≈ 2.97 vs 2.27 for LR |
| Erosion / slurry / two-phase | Preferred | Avoid unless analyzed |
| Pigging | Passes many cleaning pigs; inline-inspection tools usually need 3D/5D induction bends | Not piggable |
| Typical use | Default for process, utility and power piping | Tight skids, nozzle clearances, low-energy utility lines |
In practice, specify LR unless a layout or nozzle clearance makes it impossible. When SR is used, show it on the isometric and line list so the stress engineer models the correct flexibility and SIF, and check that the hydraulic margin covers the extra loss — the Aienginear pipe pressure drop calculator handles both elbow types.
Materials, wall thickness and marking
- Carbon steel: ASTM A234 WPB (most common), WPC — see carbon steel piping materials.
- Alloy steel: ASTM A234 WP11, WP22, WP91 for high-temperature service.
- Stainless steel: ASTM A403 WP304/304L, WP316/316L.
- Low-temperature carbon steel: ASTM A420 WPL6.
- High-yield (pipeline): MSS SP-75 / ASTM A860 WPHY grades.
- Duplex stainless: ASTM A815.
Order the end wall to match the connecting pipe (for example Sch 40 / STD, Sch 80 / XS, or a specified wall). A B16.9 fitting can carry the same pressure as straight seamless pipe of equivalent material and wall, which is why the schedule must match. Each fitting is marked with the manufacturer’s name or trademark, the material and product identification, the schedule or wall, and the size.
Receiving inspection checklist
A short dimensional check at receipt catches most fitting problems before they reach a spool. For the full NDT, proof-test and marking requirements, see the pipe fittings inspection guide.
- Check marking, heat number and material certificate (EN 10204 3.1 or as specified) against the purchase order.
- Confirm elbow type (LR/SR, 90°/45°), NPS and end wall thickness.
- Measure OD and out-of-roundness at the bevel against Table 3.
- Measure center-to-end with a square and tape from the leg centerlines; compare with the pipe elbow dimensions in Table 1 or 2 and the tolerance.
- Check off-angle Q and off-plane P on a surface plate (Table 4).
- Inspect bevel angle and root face against the welding procedure (ASME B16.25 profile unless specified otherwise).
- Look for laps, cracks, deep grinding and wall thinning on the extrados; verify minimum wall by UT if required.
- Record results on the inspection test plan before release to fabrication.
Test yourself: pipe elbow dimensions quiz
Twelve questions drawn from this guide — formulas, the NPS ½ exception, tolerances, take-out and odd-angle cuts. Answer in any order, then submit to see your score with an explanation and a link back to the relevant section for every question.
ASME B16.9 Pipe Elbow Dimensions Quiz
Frequently asked questions
What is the center-to-end dimension of a 90° long radius elbow?
It is 1.5 × NPS in inches for NPS 1 and larger. For example, an NPS 4 LR elbow has A = 6.00 in (152 mm) and an NPS 12 has A = 18.00 in (457 mm). NPS ½ is the exception and uses 1.50 in (38 mm); NPS ¾ is 1.12 in (29 mm).
What is the difference between long radius and short radius elbows?
An LR elbow has a centerline radius of 1.5 × NPS and an SR elbow has 1.0 × NPS. SR saves about one-third of the center-to-end length but causes roughly 40 % more friction loss and a higher stress intensification factor, so LR is the default in most piping specifications.
Is a 45° elbow dimension half of the 90° elbow dimension?
No. A 45° LR elbow’s center-to-end is close to A × tan 22.5° (about 0.414 A) for NPS 3½ and larger, and longer than that in small sizes. NPS 6 is 95 mm, not 114 mm.
Which standard gives pipe elbow dimensions for butt-weld fittings?
ASME B16.9 (current edition 2024) covers factory-made wrought buttwelding fittings from NPS ½ to 48, including LR and SR elbows, returns, tees, reducers and caps. Short-radius elbows were moved into B16.9 from the withdrawn ASME B16.28.
Are short radius elbows available above NPS 24?
They are not tabulated in ASME B16.9. Some manufacturers supply larger SR elbows to their own drawings, so the purchase order must define the dimensions and design basis.
Does NPS equal the outside diameter of the elbow?
Only from NPS 14 upward does the OD in inches equal the NPS number. Below NPS 14 the OD is larger — NPS 2 has an OD of 2.375 in (60.3 mm).
How do I calculate pipe cut length between two elbows?
Subtract the center-to-end of each fitting and the total root gap from the center-to-center dimension on the isometric. Two NPS 4 LR elbows 1500 mm apart with 3 mm gaps give 1500 − 152 − 152 − 6 = 1190 mm.
What is the center-to-end tolerance of an ASME B16.9 elbow?
±0.06 in (about ±1.5 mm) for NPS ½–8, ±0.09 in for NPS 10–24, ±0.12 in for NPS 26–30 and ±0.19 in for NPS 32–48. Off-angle and off-plane limits are listed separately.
Related Aienginear tools and guides
- Pipe fittings dimensions & materials (tees, reducers, caps, B16.11)
- Pipe support spacing calculator
- Steam pipe sizing calculator
- Piping specification & component calculator
- How seamless and welded pipe is made
Standards and references
- ASME B16.9-2024 — Factory-Made Wrought Buttwelding Fittings
- ASME B36.10M — Welded and Seamless Wrought Steel Pipe (pipe OD and wall)
- ASME B36.19M — Stainless Steel Pipe
- ASME B16.25 — Buttwelding Ends
- ASME B16.49 — Factory-Made Wrought Steel Buttwelding Induction Bends
- ASME B31.3 — Process Piping; ASME B31J — Stress Intensification and Flexibility Factors
- Crane Technical Paper No. 410 — Flow of Fluids Through Valves, Fittings and Pipe
This page is an engineering reference prepared by Aienginear. The pipe elbow dimensions on this page were cross-checked against the ASME B16.9-2024 tables, but always confirm critical dimensions and acceptance criteria against the controlled edition specified in your contract.
Written by Muhammad Raza
Founder of Aienginear. Engineering and digital solutions professional with 26+ years managing projects, plant shutdowns and turnarounds in oil & gas, petrochemical and power generation.
